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Nutrition 1 Part 2 > Vitamin D > Flashcards

Vitamin D Flashcards

1
Q

what form of vitamin D is cholecalciferol

A

Vitamin D3

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2
Q

What form of vitamin D is ergocalciferol

A

Vitamin D2

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3
Q

Vitamin D3 is synthesized where?

A

epidermis of the skin from UVB

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4
Q

Sources of Vitamin D3

A

fish, eggs, dairy, UVB

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5
Q

Sources of Vitamin D2

A

mushrooms, dairy

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6
Q

_____ absorbs UV photons producing provitamin D2

A

ergosterol

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7
Q

_____ has unstable bonds that rearrange with heat forming ergocalciferol

A

PREvitamin D2

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8
Q

where is provitamin d3 (7-dehydrocholesterol) synthesized

A

in the sebaceous glands of skin from cholesterol

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9
Q

what does provitamin d3 absorb

A

UV photons and is then converted to precalciferol (previtamin d3)

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10
Q

precalciferol has ____ bonds that rearrange in 2-3 days resulting in _____

A

precalciferol has UNSTABLE bonds that rearrange in 2-3 days resulting in CHOLECALCIFEROL

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11
Q

cholecalciferol diffuses from what?

A

skin, into blood

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12
Q

how is cholecalciferol transported to blood

A

by vitamin D binding protein DBP (transcalciferin)

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13
Q

dietary vitamin d in association with dietary fats in packaged into what? how?

A

into micelles with the aid of bile

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14
Q

vitamin d is absorbed how? where?

A

passive diffusion in the distal small intestine

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15
Q

vitamin d from the skin is transported how?

A

diffuses directly into the blood and id pick up by DBP for transport

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16
Q

where does vitamin d from the skin on the DBP travel

A

to the liver, but it can be picked up by other tissues (adipose, mm)

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17
Q

dietary vitamin d is incorporated into what for transport

A

chylomicrons within the enterocytes for transport

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18
Q

chyloomicron remnants deliver the vitamin D where?

A

liver

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19
Q

where else can the vitamin d in the chylomicrons be transferred to DBP for delivery?

A

to extrahepatic tissues

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20
Q

25-hydroxy vitamin D3 aka____

A

calcidiol

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21
Q

25-(OHD3) synthesized from vitamin d in the _____ by what?

A

25-(OHD3) synthesized from vitamin d in the liver by 25-hydroxylase

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22
Q

what cofactor is required for the synthesis of 25(OHD3) from vitamin d?

A

Mg

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23
Q

what is the main circulating form of vitamin d and most accurately reflects vitamin d levels

A

25-OHD3

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24
Q

1,25 dihydroxy vitamin d3 (1,25 (OH)2 D3) aka_____

A

calcitriol

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25
Q

where is 1,25 (OH)2 D3 synthesized and from what and via what enzyme

A

in the kidney, from 25-OHD3, 1-hydrozylase

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26
Q

which is the active form of vitamin D

A

1,25 (OH)2 D3

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27
Q

1,25 (OH)2 D3 OR 25-OHD3 functions as a steroid hormone

A

1,25 (OH)2 D3

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28
Q

vitamin d activity is regulated by_____

A

1-hydrozylase activity

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29
Q

1-hydroxylase is stimulated by

A

PTH
low plasma Ca
low 1,25 (OH)2 D3 [ ]

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30
Q

1-hydroxylase is inhibited by

A

high 1,25 (OH)2 D3 [ ]
high plasma Ca
high K intake

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31
Q

when 1,25 (OH)2 D3 levels are high, there is an increased conversion into _______ and conversion of 25-OHD3 into _______

A

when 1,25 (OH)2 D3 levels are high,there is an increased conversion into 1,24,25 (OH)3 and conversion of 25-OHD3 into 24,25 (OH)2

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32
Q

cholecalciferol is sotred mainly in the :

A

liver and adipose tissue

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33
Q

25-OH is store primarily in the

A

blood and muscle

34
Q

vitamin d functions as:

A

steroid hormone

35
Q

Vitamin d actions are mediated through what

A

VDR

36
Q

inside the cell 1,25 (OH)2 + VDR bind to what

A

VDREs

37
Q

1,25 (OH)2 + VDR + VDREs do what

A

initiate a cascade of molecular interaction that modulate the transcription of specific genes.

38
Q

Vitamin D is essential for the efficient utilization of ______ in the body

A

calcium

39
Q

Parathyroid gland secrets PTH when calcium levels are ____

A

low

40
Q

PTH stimulates the activity of

A

1-hydroxylase in the kidney

41
Q

PTH of 1-hydroxylase int he kidney results in

A

increase conversion of 25-OH to the active calcitriol

42
Q

increased calcitriol production restores normal serum calcium levels in what 3 ways

A
  • activation vitamin d transport system
  • stimulating production and maturation of osteoclasts
  • increasing the reabsorption of calcium in the distan renal tubules
43
Q

PTH increases or decreases calcium mobilization

A

increases

44
Q

the process of calcium homeostasis is controlled by

A

negative feedback loop - where increasing serum calcium and calcitriol levels inhibit PTH secretion and calcitriol production

45
Q

______ is required for the differentiation of many cell types

A

calcitriol

46
Q

calcitriol is required for the differentiation of WHAT cell types

A

skin epidermis
premyeloid WBCs, stem cells into macrophages and monocytes
stem cell monocytes in the bone marrow into mature osteoclasrs

47
Q

calcitriol inhibits what cell type proliferation

A

fibroblasts, keratinocytes, lymphocytes

abnormal intestinal lymphatic, mammary and skeletal cells

48
Q

true or false: calcitriol can induce cell apotosis

A

true

49
Q

low vitamin d levels are associated with increasde risk of developing and dying from several cancers including

A 
prostate
breast
colon
ovarion
non-hodgkins lymphoma
50
Q

________ is a potent immune system modulator

A

1,25 OH2

51
Q

VDR is expressed by most cells including

A

t cells, APCs

52
Q

inadequate vitamin d levels are linked with what other diseases

A

RA, crohns, MS, DM 1

53
Q

____ plays a role in insulin secretion

A

1,25 OH2

54
Q

T or F, adequate Vitamin D levels are important for decreasing risk of high BP

A

true

55
Q

Vitamin D metabolites are excreted in the

A

feces (70%) and urine

56
Q

the amount of vitamin d produced in the skin depends on what

A 
season
level of latitude
time of day
degree of pigmentation
age
57
Q

in vitamin D deficiency ______ absorption cannot be increased enough to satisfy the bodys needs

A

calcium

58
Q

when calcium absorption is not enough to satisfy the bodys needs _____ is increase and calcium is mobilized from the skeleton to maintain normal serum calcium levels

A

PTH

59
Q

In children vitamin D deficiency is called

A

rickets

60
Q

signs and sx of rickets

A 
bone mineralization defects
dental abnormalities
growth retardation
muscle weakness
seizures
61
Q

bone minerailzation defects in rickets result in

A 
enlarged joints
legs bow, knees knock
spine becomes curved
pelvic and thoracic deformities
delayed closure of fontanels
62
Q

in adults vitamin d deficiency is called

A

osteomalacia

63
Q

signs and sx of osteomalacia

A 
bone mineralization defects
mm weakness
low back pain/ aches
fatigue
sweating
64
Q

increased risk of vitamin D deficiency in

A 
insufficient sun exposure
exclusively breast fed infants
dark skin
aging
obesity
fat malabsorption syndromes
65
Q

people with dark coloured skin synthesize LESS OR MORE vitamin D than light colour skin

A

less

66
Q

the elderly have a INCREASED OR REDUCED capacity to synthesize vitamin D when exposed to UVB

A

reduced

67
Q

once vitamin d is synthesized in the skin or ingested, it is deposited _____

A

body fat stores

68
Q

the vitamin D in body fat stores makes vitamin d LESS OR MORE bioavailable

A

less

69
Q

vitamin D supplementation is clinically indicated for

A

osteoporosis

cancer prevention

70
Q

the preferred form for supplementation is

A

cholecalciferol (D3)

71
Q

hypervitaminosis D induces what

A

abnormally high serum calcium levels

72
Q

abnormally high serum calcium levels could result in

A

kidney stones

calcification of soft tissues

73
Q

certain medical conditions can increase the risk of hypercalcemia in response to vitamin D…..what are they

A 
hyperparathyroidism
sarcoidosis
TB
lymphoma
* increased caution should be taken when supplementing these individuals
74
Q

which is more toxic D2 or D3

A

D2

75
Q

T OR F - excessive sun exposure is not associated with risk of vitamin d toxicity

A

true

76
Q

signs and sx of hypervitaminosis D

A 
hypercalcemia hypercalciuria
loss appetite, constipation, n/v
mm weakness
hypertension and cardiac arrythmias
calcification of soft tissues
renal dysfxn
mental confusion
death
77
Q

Vitamin D increased the intestinal absorption of what two minerals

A

Ca and P - promotes deposition into bone

78
Q

what mineral is required for the conversion of vitamin d3 to 25(OH)D3

A

Mg

79
Q

synthesis of what vitamin dependent proteins are stimulated by 1,25OH2

A

Vitamin K

80
Q

what is the best indicator of vitamin d status

A

serum 25 (OH)

Nutrition 1 Part 2 (23 decks)

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